Electricity Cost Calculator (UK)

Want a quick, realistic estimate of your electricity costs? The UK electricity bill has two core ingredients: how much electricity you use, and how your tariff charges for it. Most domestic tariffs charge a unit rate for every kWh you consume, plus a standing charge each day.

If you already know your monthly electricity usage (in kWh) — often shown on your bill or in your supplier app — you can estimate annual costs by multiplying that usage by the tariff’s unit rate, then adding the standing charge for the year. This gives you an “apples to apples” number for comparing tariffs.

Step 1: Find your monthly usage (kWh)

Check your latest bill for consumption over a month or a quarter. If you only have an annual figure, divide by 12 to get a monthly estimate. If you’re unsure, start with a rough guess — the calculator is designed to give you a clear comparison quickly.

Step 2: Understand unit rate vs standing charge

• Unit rate: billed per kWh. Higher usage makes this more important.
• Standing charge: billed per day. Lower usage makes this more important because it’s fixed.

Step 3: Estimate annual cost

This is the same approach we use in the Octopus Savings Calculator — but instead of asking you to copy unit rates manually, we fetch live rates and standing charges directly from Octopus’s official API for your postcode region.

If Octopus looks cheaper, switch with £50 credit

Once you’ve seen your estimate, you can switch to Octopus using a referral link and receive credit after you join.